Solid formulation

ABSTRACT

The formation of undesirable sludge in the course of spraying a solution or dispersion of a water-soluble or water-dispersible solid or a structured gel formulation is reduced by the incorporation in the formulation of a low-density solid particulate material having a density of less than one and a diameter of less than the spray nozzle filter through which it will pass. The low-density solid particulate material is preferably a hollow glass or plastic particle having a density of less than 0.8 g/cm 3 . The invention is particularly applicable to agrochemical formulations.

This invention relates to a solid or structured gel formulation and inparticular to a solid or structured gel formulation of a water-solubleor water-dispersible material suitable for aqueous spray applicationafter dispersion or dissolution in water. The invention further relatesto a method of reducing sludge formation in the course of spraying asolution or dispersion of a water-soluble or water-dispersible solid orstructured gel formulation.

Floating granules are known and used for example in paddy watertreatments to provide a slow dispersion of material over a passage oftime. Such granules are applied directly to the paddy field, as opposedto being tank mixed, and in consequence do not give rise to sludgeproblems.

In Zasso Kenkyu (1995), 40 (2), 80-6 there is disclosed a study of anaproanilide formulation taking the form of a wettable powder housed ina water-soluble bag and containing hollow glass floating carrierparticles. The water-soluble bag containing the formulation is intendedfor direct application to paddy water. It was concluded that when theconcentration of the carrier was high, the formulation floated on thewater surface until the wettable powder completely diffused into waterand the amount of naproanilide released from the formulation into waterwas large. If the concentration of the carrier was low, the entire bodyof the formulation sank soon after the film dissolved in water resultingin low release of naproanilide. In tests of biological activity it wasconcluded that a wettable powder packed in a water soluble filmcontaining 20% floating carrier has potential as a formulation whichcould reduce the labour of herbicide application in paddy fields butthat when the carrier content was less than 14%, little amount ofnaproanilide diffused in the water and the herbicidal efficacy wasextremely low.

The present invention is applicable to any solid or structured gelformulation suitable for aqueous spray application after tank mixdispersion or dissolution. Whilst the present invention is notrestricted to any one particular field, such solid or structured gelformulations are typically used for aqueous sprays in agriculture,public health and animal health. Thus the active ingredient may forexample be a herbicide, insecticide, nematocide, fungicide or plantgrowth regulator. Alternatively the granule may be used to carry anauxiliary agent such as a wetter or other adjuvant.

Active ingredients or auxiliary agents suitable for application by meansof an aqueous spray may be formulated in a wide variety of ways. Thepresent invention relates to solid water-soluble or water-dispersibleformulations such as granule formulations (sometimes also referred to aswater-soluble or water-dispersible grain formulations or wettablegranules). The present invention is not however limited to granuleformulations its advantages may also be apparent in other forms of solidformulation such as “cast tapes” (as described for example inInternational application No 96/02947 and in GB 2095558), flakes,wettable powders or tablets. The present invention also relates tostructured gel formulations, for example structured gel formulationssuitable for incorporation in a water-soluble bag and containing solidwater-dispersible material.

Such solid or structured gel formulations (and in particular structuredgel formulations when housed in a water-soluble bag) have a number ofadvantages as compared with liquid formulations. Such advantages includefor example reduced transport costs, reduced operator exposure andreduced residue contamination of containers. A solid formulation orwater-soluble bag containing a structured gel formulation may reduceresidue formation to the extent that the use of a disposable containeris acceptable.

A wettable, dispersible or water-soluble solid or structured gelformulation normally consists of an agrochemical or other ingredientsuitable for application by aqueous spray incorporated with a solidinert filler which may be water-soluble or water-dispersible. Theagrochemical or other ingredient may be a solid or liquid and may bewater-soluble or water-dispersible. Auxiliary agents such assurfactants, activity enhancers, anti-foams and stabilisers arefrequently used and may be incorporated in the same solid or structuredgel formulation with the active ingredient or may be formulatedseparately or may be added at the tank mix stage.

Solid or structured gel formulations such as granules may be formed by avariety of techniques, including for example pan granulation, spraydrying, agglomeration and extrusion. Techniques for providing solid“cast tapes” are illustrated in GB 2095558 and in our Internationalapplication No 96/02947. Techniques for providing structured gelformulations are illustrated for example in WO 96/03871.

In use, the solid or structured gel formulation is added to water toform a solution or dispersion which is then applied as a spray, forexample as a spray application to plants. In agrochemical use forexample, the solid or structured gel formulation is typically mixedimmediately prior to spraying with water in a tank containing from about20 liters for a knapsack sprayer to about 100 to 2000 liters of waterfor a commercial spray tank. The structured gel formulation mayconveniently be housed in a water-soluble bag prior to addition towater. Solid formulations are more normally added directly to the waterbut may also be housed in a water-soluble bag if desired. Whilst suchspray tanks are generally provided with some means of agitation, such asmechanical stirring or pumped circulation of the water, the degree ofmixing within the tank may be relatively inefficient or the solid orstructured gel formulation itself may be inherently difficult todisperse, particularly for example if the formulation has been allowedto age. In particular there may be specific zones within the tank (“deadzones”) in which the level of agitation is especially poor. In practicetherefore effective dispersion of insoluble or partially or slowlysoluble materials may not be achieved and an insoluble solid sludge maybuild up in such dead zones within the tank during the time-scale ofspray application. Once a sludge is allowed to start to build up, it maybecome compacted and much harder to re-disperse, even with theapplication of effective agitation. Even if the sludge is re-dispersed,it may still form relatively large agglomerates of particles which maytend to block the spray nozzles or filters. Furthermore, the formationof a sludge represents a removal of active material from the aqueousphase leaving the spray nozzle. Thus even if the sludge is eventuallydispersed and leaves no residue, the concentration of active material inthe spray will be less in the initial stages than in the later stageswhen the sludge is beginning to break up and pass through the nozzle.Sludge formation can therefore lead to uneven distribution of the activeingredient in the spray and poor biological utilisation of activematerial. Sludge left in the spray tank after spraying is completed maycause contamination and disposal problems. In general the formation ofsludge in the spray tank is a well-recognised problem which may beassociated with the use of solid or structured gel formulations. Onesolution to this problem would of course be to provide more efficientagitation within the mixing tank but the cost involved makes thisunattractive and a solid or structured gel formulation having reducedsludge formation in conventional spray tanks is to be preferred.

We have now found that the problem of sludge formation may be mitigatedif the density of the solid or structured gel formulation is reduced bythe incorporation therein of a solid particle hang a density of lessthan one. Since the solid particle should not block the nozzle it shouldhave a diameter less than that of the spray nozzle. Furthermore since inuse the spray nozzle is generally protected from blockage by a suitablefilter, the particle should preferably have a diameter of less than ofthe spray nozzle filter through which it will pass.

Thus according to the present invention there is provided a method ofreducing sludge formation in the course of spraying a solution ordispersion of a water-soluble or water-dispersible solid or a structuredgel formulation which comprises incorporation in said solid orstructured gel formation a low-density solid particulate material havinga density of less than one g/cm³ and a diameter of less than the spraynozzle filter through which it will pass.

According to a further aspect of the present invention there is provideda solid or a structured gel formulation suitable for use in such amethod comprising a low-denay solid particulate material having adensity of less tan one g/cm³ and a diameter of less than the spraynozzle filter through which it will pass.

The solid or structured gel formulation will normally bewater-dispersible since the problem of sludge formation is clearly lessserious with water-soluble solid or structured gel formulation, althougheven water-soluble solid or structured gel formulations may give rise tosludge formation if the dissolution of the solid is slow compared withthe of spraying. Thus for example a typical solid formulation of theinvention is a water-dispersible granule, powder, flake, tablet or cast,tape and comprises a water-dipersible or water-soluble agrochemical oragrochemical auxiliary agent and a water-dispersible carrier. A typicalstructured gel will contain water-dispersible material held within thegel structure.

Problems of sludge formation are most commonly associated with the useof a water-dispersible filter. Many such filters are known in the artand a wide commercial choice of filter is available. Examples of typicalwater-dispersible filters include talc, silica, kaolin, pyrophylite,powdered limestone, acid clay, ditamaceous earth, gypsum, pumice, shellpowder, mica and silicates. Dense water-dispersible fillers such as talcmay give rise to particular problems by propelling granules rapidly tothe floor of the spray tank to form difficult sludges.

The low-density solid particular material having a density of less thanone g/cm³ preferably has a density of less than 0.8 g/cm³ for exampleless than 0.3 g/cm³ and preferably less than 0.2 g/cm³ for example about0.1 g/cm³. Unless otherwise stated the units of density used herein inrespect of the low-density solid particulate material are g/cm³. Suchlow densities are conveniently achieved by use of a hollow particle, andthe solid particulate material having a density of less than one ispreferably a hollow particle, for example a hollow glass or plasticsparticle. An especially suitable material comprises expanded polymermicrospheres which in general have a lower density than hollow glassparticles. Suitable expanded polymer spheres are available under thetrademark “Dualite” from UBC (Chem) Limited, a product of Pierce &Stevens. A suitable polymer material is a polyvinylidene chlorideacrylonitrile co-polymer, an acrylonitrile co-polymer a polystyrenepolymer or a poly(vinylidene chloride) polymer. The low-density solidparticulate material may be supplied with inorganic filler particles,for example calcium carbonate, embedded in the surface. Whilst this isnot believed to be essential for the purposes of the present invention,no adverse consequences have been observed if a surface-coated productis used.

The low-density solid particulate material preferably passes completelythrough a BS standard 100 mesh sieve (BS No 410/1986-150μ), and forexample has a volume mean diameter (D(4,3)) below 100 microns, forexample below 50 microns. Preferably the material has a volume meandiameter between 20 to 50 microns, for example from 20 to 30 microns.Finer particles may be used if desired but may be more difficult toformulate satisfactorily. Particles having a diameter between 50 and 100microns or more have been found to be effective in achieving sludgereduction in the method of the invention but may cause filter blockagein those applications in which a relatively fine filter is required. Forsuch applications, it is especially preferred that the low-density solidparticulate material has a volume size distribution such that 5 volumepercent has a size no greater than about 60 microns and more preferablyno greater than about 50 microns.

The proportion of low-density solid particulate material to be useddepends to some extent on the overall density of the solid or structuredgel formulation and in particular the nature of the water-dispersiblefiller in the solid or structured gel formulation. In general thelow-density solid particulate material may comprise from about 0.01 toabout 10% by weight of the total solid or structured gel formulation andpreferably from about 0.1 to about 6% by weight, for example from 0.1 to2% by weight of the total solid or structured gel formulation. There isclearly no particular advantage in including a greater proportion oflow-density solid particulate material than that required to make thesolid or structured gel formulation float. Furthermore, we have foundthat it is not necessary, and indeed may be positively undesirable toinclude sufficient low-density solid particulate material that the solidor structured gel formulation actually floats. Thus although a solid orstructured gel formulation which floats prior to dissolution in thespray tank may be used, it is preferred that sufficient of thelow-density particulate material is used such that the solid orstructured gel formulation sinks slowly on addition to water i.e. thatthere is added less low-density solid particulate material than thequantity which would be required to make the water-soluble orwater-dispersible solid or a structured gel formulation float in water.If a solid or structured gel formulation is used in a water-soluble bag,the bag and content may of course initially float when added to water,provided that when the contents are eventually released from the bagthey sink slowly.

Very low density granules are also not generally preferred for practicalreasons because they tend to exhibit poor packing characteristics. Thepacking of a solid formulation may be measured in terms of its “tapdensity” which is the volume occupied by the solid formulation in acontainer (such as a measuring cylinder) after gentle tapping to allowthe solid to settle divided by the weight of the solid. A tap density ofbetween 0.25 to 0.6 g/ml is preferred. Granules having a tap density ofabout 0.35 g/ml will generally just float in water and the tap densityis more preferably from about 0.35 to about 0.5 g/ml for granules of theinvention. Other formulations such as cast tapes exhibit much betterpacking than granules and the tap density of cast tapes may therefore behigher. Since there are essentially no air spaces in cast tapeformulations, tapes will normally just float at a “tap density” of one(i.e. the “tap density” is the same as the true density). Typical casttapes of the invention may have a density in the range from 0.5 to 1.7g/ml and preferably 1 to 1.6 g/ml. At least a part of the function ofthe low-density solid particulate material is believed to be a result ofthe reduction in the overall density of the solid or structured gelformnulation, for example the granule or tape, which prevents it sinkingrapidly to the floor of the spray tank immediately on addition. However,although the function of the low-density solid particulate material inreducing sludge is poorly understood, it is believed to be more complexthan a simple reduction in density. Thus for example individualparticles of low-density solid particulate material are believed tobreak away from the surface of the dispersing solid or structured gelformulation and rise rapidly to the water surface, thereby facilitatingthe break-up of the surface of the solid or structured gel formulationand creating additional turbulence in the spray tank.

The solid or structured gel formulation, such as the granule or casttape, may contain one or more active ingredients or auxiliary agents andmay contain one or more additional components such as a synergist, ahumectant, a dye, a pigment, a corrosion inhibitor, a wetting agent or adispersing agent. It will generally be desirable, but not essential, toinclude a wetting agent or a dispersing agent in the granule.

Wetting or dispersing agents include cationic, anionic or non-ionicagents. Suitable cationic agents are quaternary ammonium compounds, forexample, cetyltrimethylarnmonium bromide. Suitable anionic agents aresoaps, salts of aliphatic monoesters of sulphuric acid (for example,sodium lauryl sulphate), and salts of sulphonated aromatic compounds(for example, sodium dodecylbenzenesulphonate, sodium, calcium orammonium lignosulphonate, butylnaphthalene sulphonate, and a mixture ofsodium diisopropyl- and triisopropylnaphthalene sulphonates).

Suitable non-ionic agents are the condensation products of ethyleneoxide with fatty alcohols such as oleyl or cetyl alcohol, or with alkylphenols such as octyl- or nonylphenol and octylcresol. Other non-ionicagents are the partial esters derived from long chain fatty acids andhexitol anhydrides, alkyl glucosides, polysaccharides and the lecithinsand the condensation products of the said partial esters with ethyleneoxide.

The low-density solid particulate material may be incorporated into thesolid or structured gel formulation along with the other solidingredients and using conventional methods known to those skilled in theart for preparing such formulations.

The invention is illustrated by the following Examples in which allparts and percentages are by weight unless otherwise stated.

EXAMPLE 1

Granules containing 50% by weight of the commercial insecticidepirimicarb were prepared by conventional extrusion techniques exceptthat there was added 5% by weight of a low-density solid particulatematerial commercially available under the trademark “Dualite” M6033AEconsisting of expanded polyvinylidene chloride acrylonitrile copolymerspheres having a density of about 0.13, a mean particle size of 25microns and a size distribution such that 5% by volume had a diametergreater than 43 microns. A commercially available granule (950 g),“Pirimor” 50 WG (“Pirimor” is a trademark of Zeneca Limited and containsprimicarb as active ingedient) was ground to a powder and low-densitysolid particulate material (50 g) was added. Water (140 g) was added andthe mixture was blended in a Hobart mixer to form a smooth paste whichwas granulated by extrusion through a 1 mm sized screen. The resultantgranules were dried at 50° C. for 20 minutes.

The granules of the invention were compared with granules prepared inexactly the same way by grinding “Pirimor” 50 WG and subsequentre-granulation but in which the low-density solid particulate materialwas omitted.

The granules were added to 800 liters of water in a commercial HorstineFarmery 1000 liter tank agricultural spray tank with conventionalagitation supplied by a re-circulation pump to give a theoreticalconcentration of active ingredient (pirimicarb) equivalent to 0.44 g/lassuming the product completely dispersed. Both the granules of thepresent invention and granules not containing the low-density solidparticulate material sank on addition to water. The resultant dispersionwas sprayed through an elliptical nozzle of approximately 450 microndiameter (more specifically defined as BCPC Fan 110° at 0.8 liters perminute and 3 bar pressure) protected by a 150μ micron filter. Theuniformity of the spray was determined by measuring the concentration ofpirimicarb in the spray solution at intervals corresponding to theremoval by spraying of 100 liter aliquots from the tank. The results aregiven in Table 1 from which it will be seen that a significantly moreuniform spray gradient is obtained using the granules of the inventioncompared with granules not containing low-density solid particulatematerial.

After spraying was completed the residue in the tank was collected.Visual inspection showed that the sample which contained the low-densitysolid particulate material had left a slight residue on the base of thetank but this was significantly lower than from the control experiment.

TABLE 1 Granule of the invention Corresponding granule containinglow-density without low-density solid particulate solid particulatematerial material Concen- Concen- tration Deviation from trationDeviation from Liters of pirimicarb theoretical of pirimicarbtheoretical Sprayed (g/l) concentration (g/l) concentration 0 0.46 0.020.43 −0.01 100 0.47 0.03 0.44 0.00 200 0.48 0.04 0.43 −0.01 300 0.580.14 0.43 −0.01 400 0.59 0.15 0.42 −0.02 500 0.55 0.11 0.48 0.04 6000.63 0.19 0.58 0.14 700 0.60 0.16 0.73 0.29 800 0.59 0.15 0.82 0.38

EXAMPLE 2

Granules containing 50% by weight of the herbicide fluazifop-p-butyl and5% by weight of “Dualite” M6033 AE were prepared in the same manner asin Example 1 from a commercially available granule. A controlformulation was prepared which did not contain the “Dualite” M6033 AEbut was identical in respect of the other formulation ingredients. Thesamples were sprayed in a 1000 liter Horstine Farmery agricultural spraytank at a nominal concentration of 1.875 g/l, which was formed by theaddition of 3 kilos of the granules to 800 liters of water. Samples ofthe spray solution showed that the inclusion of the “Dualite” M6033 AEhad improved the concentration gradient compared to the control sample.Examination of the base of the tank after spraying was complete showedthat there was no observable residue present from the sample containing“Dualite” M6033 AE whilst the control sample left a residue which wasestimated to contain 50% by weight of the starting granules.

EXAMPLE 3

Granules containing 50% by weight of the commercial insecticidepirimicarb were prepared by conventional extrusion techniques, exceptthat there was added 2% by weight of low density solid particulatematerial commercially available under the trademark “Dualite” M6033AE asused in Example 1.

A commercially available granule (735 g), “Aphox” 50 WG (“Aphox” is atrademark of Zeneca Limited) was ground to a powder, and low densitysolid particulate material (15 g—to provide 2% w/w “Dualite” in thefinal granule) was mixed in. Water (180 g) was added and the mixtureblended in a Hobart mixer to form a smooth paste which was granulated byextrusion through a 1 mm sized screen. The resultant granules were driedat 50° C. for 20 minutes. This batch procedure was repeated severaltimes in order to produce the quantity of granules required for testing.The above procedure was repeated with “Aphox” granules (720 g) and lowdensity solid particulate material (30 g), to produce “Aphox” 50 WGcontaining 4% w/w “Dualite”. Finally, a control sample was produced inexactly the same way by grinding “Aphox” 50 WG and subsequentre-granulation but in which the low density solid particulate materialwas omitted. All granules sank on addition to water.

Sludge formation was evaluated using a laboratory sludge test which hasbeen found to simulate commercial large scale spray application. Thetest, designed to measure the amount of sludge that is left in thebottom of a glass beaker after the granules have been allowed todisperse without agitation for 10 minutes was carried out as follows:

Sludge Test

A dry 600 ml glass beaker is weighed (X g) and about 300 g of water isadded. The water will normally be from a sink tap and it is necessarythat the temperature of the water is recorded. About 50 g (Z g) ofgranule product is weighed accurately and added to the water. Thegranules are left immersed in the water for 10 minutes withoutagitation. The contents of the beaker are poured into an effluentcontainer, after allowing 30 seconds for drainage of the residue fromthe upturned vessel. The beaker is then transferred to an oven at 50° C.in order to dry the wet residue. After 30 minutes (or when the residueis dry) the mass of the glass beaker plus residue (W) is determined.

The initial sludge residue (%) is then quoted as: (W−X/Z)×100

The sludge test results for the above WG formulations are given in Table2:

TABLE 2 Low Density particulate Material (%) Sludge (%) Temp (° C.) 03.0 21.5 2 2.8 21.5 4 1.6 21.5

Spray tests on the above WG formulations were carried out as follows:

Spray Test

The test granules (1 kg) were added to 400 liters of water in acommercial Horstine Farmery 1000 liter agricultural spray tank withconventional agitation supplied by a re-circulation pump. The granulessank to the base of the tank and dispersed in the agitated water. Theresultant dispersion was sprayed through four elliptical nozzles ofapproximately 450 micrometer diameter. Two of the four nozzles wereprotected by 150 micrometer filters, and the other two by 300 micrometerfilters. The uniformity of the spray was determined by taking 250 mlspray samples at intervals corresponding to the removal by spraying of100 liter aliquots from the tank. The spray samples were visuallyinspected for turbidity and graded by comparing to 3 pre-preparedcalibration spray samples, where 10/10 was the grade given for anexpected spray concentration (0.63 g/250 ml), 5/10 was the grade givenfor a spray concentration half that of the expected spray concentration(0.31 g/250 ml) and 20/10 was the grade given for a spray concentrationtwice that of the expected spray concentration (1.25 g/250 ml).

The results of the spray tests are shown in Table 3 from which it can beseen that a significantly more uniform spray gradient is obtained usingthe granules of the invention compared with the granules not containingthe low density solid particulate material.

TABLE 3 Granule of the invention Corresponding granule Volume containing4% w/w low density without low density solid Sprayed solid particulatematerial particulate material (liters) Grade Grade  0  9/10  6/10 10010/10  6/10 200 10/10  7/10 300 10/10 15/10 400 10/10 20/10

After spraying was completed the spray nozzles were checked forblockages and residue and the base of the spray tank inspected forsludge residue. The results are shown in Tables 4 and 5 respectively.

TABLE 4 Granule of the Corresponding granule invention containingwithout low density Filter 4% w/w low density solid particulate Sizesolid particulate material material Nozzle (μm) Assessment Assessment 1300 none none 2 150 trace 5% residue 3 300 trace trace 4 150 5% residue30% residue

TABLE 5 Low Density Solid Sludge Residue Temperature (%) (%) (° C.) 05-10 25 2 2 24 4 1 25

Bioefficacy Test

Glasshouse tests confirmed that the polymeric low-density,microparticles do not adversely affect the bioefficacy of “Aphox” WGformulations. Standard glasshouse aphid contact/residual tests carriedout on a mixed age population of R2 Myzus persicae showed that there-extruded “Aphox” WG formulation with “Dualite” M6033AE, demonstratesaphicidal activity that is not statistically different from thecommercial “Aphox” 50 WG formulation.

EXAMPLE 4

A solid formulation in the form of a water dispersible tape comprisingapproximately 5% by weight of lambda-cyhalothrin and 0.16% by weight oflow density solid particulate material commercially available under thetrademark “Dualite” M6033AE as used in Example 1 was prepared accordingto the following procedure:

A mixture of polyvinylpyrrolidone polymers of molecular weights 10,000(5.80 g) and 44,000 (2.80) was added to water (19.90 g) and stirreduntil all the polymer had dissolved. “Morwet” EFW (0.20 g) an anionicnaphthalene sulphonate wetting agent from Witco, and Microtalc filler(17.10 g) a hydrated magnesium silicate with a mean particle size ofapproximately 7 micrometers, were added and stirred until all the powderwas completely dispersed. Sorbitol (2.50 g), silicone antifoam (0.15 g),lambda-cyhalothrin (1.50 g) and “Dualite” M6033 AE (0.05 g) were finallymixed in and stirred for a further 15 minutes to ensure completedispersion.

The viscous film-forming slurry was cast onto a polymer film substrate,using a ‘doctor blade’ set at a blade height of 0.75 mm. The cast tapewas dried for 2 hours in an oven maintained at 50° C. and then strippedfrom the substrate as a coherent tape of thickness 0.31 mm. 10 g of thetape was then cut into 20 squares of dimension 20×20 mm. The density ofthe tape was 1.426 gm⁻³ (greater than the density of water). The tapesamples were then spray tested in a Coopler Pegler CP3 knapsack sprayer,The tapes were added to the spray tank which was filled with 4 liters ofwater at 9.5° C., and allowed to soak for 1 minute. The tank was thentopped up to 20 liters of water and shaken 10 times from side to side,prior to spraying. Spray samples were examined when the water level inthe tank was 20, 16, 12, 8, 4 and 1 liter. No nozzle blockage occurredduring spraying, the spray samples examined were essentially uniform incolour and no tape residue was present in the base of the tank whenspraying was complete.

In comparison, spray testing of a control water dispersible tape sampleprepared in exactly the same manner but in which the “Dualite” powderwas omitted showed a sludge residue of 5-10% at the base of the tank.

EXAMPLE 5

A gel formulation comprising 62.5% w/w fluazifop-P-butyl was preparedaccording to the procedure described in Example 1 of Internationalapplication WO 96/03871. The composition of the gel was as follows:

Component Amount (% w/w) Fluazifop-P-butyl 62.5 (amount of activeingredient present) Methyl oleate to 100 Silica power (surface area 200m²/g) 2.0 BRIJ 96 1.0 Ethylene glycol 1.0 SYNPERONICA4 2.0 SOPROPHOR 4D384 2.0 AEROSOL OT-B 2.5 Phenyl sulphonate CALX 1.0

(BRIJ, SYNPERONIC, SOPROPHOR and AEROSOL are trademarks or tradenames)The ingredients listed were sequentially added (in the order listed) andhigh shear mixed to produce a homogeneous gel. The low-density solidparticulate material “Dualite” M6033AE (0.8 g) was then added to thefluazifop-P-butyl 62.5 gel formulation (39.2 g) and stirred in using aspatula to produce a homogeneous gel comprising 2% by weight oflow-density solid particulate material. The formulation was then left tostand overnight, to allow the gel structure to reform.

When added to water, the gel formulation according to the invention sankslowly. When tested according to the sludge test procedure described inExample 3, the gel formulation according to the invention produced 0.7%sludge when immersed in water at 21° C., whilst the comparison gel notcontaining low-density solid particulate material produced 7.6% sludge.

EXAMPLE 6

A tablet formulation containing “Fordacal” 30 (1.8 g), a powdercomprising crystalline calcium carbonate of mean particle size 7micrometers, and “Igepal” CO-990 (0.1 g), a nonyl phenol ethoxylatesurfactant, and “Dualite” M6017 AE (0.1 g), polymeric microsphereshaving a mean particle size of 70 micrometers, was produced by mixingthe three powder components and compressing in a ‘Specac’ tabletcompactor for 1 minute under a force of 10 tons. The resultant tablet(comprising 5% by weight of the polymeric microspheres) had a diameterof 25 mm and a thickness of 2.1 mm. A control tablet, comprising“Fordacal” 30 (1.9 g) and “Igepal” CO-990 (0.1 g) and no “Dualite”component, was also produced in a similar manner.

The two tablets were immersed in separate 400 ml beakers containingwater (300 ml) at a temperature of 22° C. and both sank. After 2 minutesof soaking the tablet containing the “Dualite” microspheres showedfaster disintegration and dispersion in comparison to the controltablet.

EXAMPLE 7

A wettable powder (WP) formulation (comprising 1.5% by weight oflow-density microparticles) contained in a water soluble bag wasprepared as follows. Pre-ground N-phosphonomethylglycine acid powder(500 g, active ingredient content), “Dualite” M6033 AE (15 g) andpre-ground “Igepal” CO990 (to 1 kg), a nonyl phenol ethoxylatesurfactant, were mixed to form a homogeneous blend. The powder blend(113 g) was weighed into a water soluble bag (Chris Craft Grade M7031,38 micrometer thick sachets of dimension 3×3 inches) and heat sealedusing an impulse heat sealer. Two similar bags were prepared and storedin sealed polythene/polyamide laminated outer packs.

A further two bags were prepared in exactly the same manner as aboveexcept that the low-density “Dualite” powder was omitted.

Spray tests on the formulations were carried out as follows:

A commercial Horstine Farmery 1000 liter agricultural spray tank wasfilled to 100 liters with water at 20° C. The water was agitated bymeans of a re-circulation pump whilst the sachets, added through the topopening of the tank, were allowed to rupture under the action of thewater. Once the sachets had ruptured, the wettable powder which wasreleased sank. After mixing for a further 2 minutes, the water wastopped up to 400 liters and allowed to mix for a further 1 minute priorto spraying.

The bags containing the formulation of the invention resulted in gooddispersion of the product with no tank or sieve residue. In the case ofthe control samples (without added “Dualite”), some 50% of the productremained as residue in the tank.

EXAMPLE 8

An “Aphox” granule formulation comprising 2% w/w of a larger diameter,low-density solid particles—“Dualite” M6017 AE, consisting of expandedpolyvinylidene chloride acrylonitrile copolymer spheres having a densityof 0.13 g/cm³ and a mean particle size of 70 microns—was preparedaccording to the procedure described in Example 3. Spray tests carriedout according to the procedure described in Example 3 gave no nozzleblockage during spraying, produced spray samples that were essentiallyuniform in colour and showed only a small amount of residue (less than2%) at the base of the tank on completion of the spray cycle.

EXAMPLE 9

A solid formulation in the form of a water dispersible tape was preparedas follows: Polyvinylpyrrolidone polymer of molecular weight 10,000(17.2 g) was added to water (39.9 g) and stirred until all the polymerhad dissolved. “Morwet” EFW (0.4 g) an anionic naphthalene sulphonatewetting agent from Witco, and Microtalc filler (34.2 g) a hydratedmagnesium silicate with a mean particle size of approximately 7micrometers, were added and stirred until all the powder was completelydispersed. Sorbitol (5.0 g) and silicone antifoam (0.3 g), and “Tecfil”T85LD (3.0 g), an alumino silicate glass from Filtec Ltd, composed ofhollow, free flowing spheres of density 0.5 g/cm³ with at least 99% ofthe particles less than 85 micrometer in diameter, were finally mixed inand stirred for a further 15 minutes to ensure complete dispersion.

The viscous film-forming slurry was cast onto a polymer film substrate,using a ‘doctor blade’ set at a blade height of 0.75 mm. The cast tapewas dried for 2 hours in an oven maintained at 50° C. and then strippedfrom the substrate as a coherent tape comprising 5% by weight of glassmicrospheres. A control water dispersible tape sample, was prepared inexactly the same, but without the addition of the low-density “Tecfil”T85LD powder. The two tape samples were immersed in separate 400 mlbeakers containing water (300 ml) at a temperature of 22° C. Both tapessank, but the tape containing the “Tecfil” microspheres immediatelyshowed release of low-density microspheres on soaking which resulted infaster disintegration and dispersion in comparison to the control tape.

What is claimed is:
 1. A method of reducing sludge formation in thecourse of spraying a solution or dispersion of a water-soluble orwater-dispersible solid or a structured gel formation of awater-dispersible or water-soluble active agent for use in agriculture,public health or animal health or an auxiliary agent for use in suchfields which method comprises a) incorporating in said solid orstructured gel formulation a low-density solid particulate materialhaving a density of less than one g/cm³ and a diameter of less than thespray nozzle filter through which it will pass b) adding said solid orstructured gel formulation to water in a spray tank to form a solutionor dispersion of the active agent or auxiliary agent and c) applyingsaid solution or dispersion to plants as a spray via a spray nozzlefilter and spray nozzle.
 2. A method according to claim 1 wherein thewater-soluble or water-dispersible solid formulation is awater-dispersible granule or cast tape.
 3. A method according to claim 1wherein the low-density solid particulate material is a hollow glass orplastics particle having a density of less than 0.8 g/cm³.
 4. A methodaccording to claim 4 wherein the low-density solid particulate materialhas a density of less than 0.2 g/cm³.
 5. A method according to claim 1wherein there is added less low-density solid particulate material thanthe quantity which would be required to make the water-soluble orwater-dispersible solid or a structured gel formulation float in water.6. A method according to claim 1 wherein the low-density solidparticulate material comprises from 0.01 to about 10% by weight of thetotal solid or structured gel formulation.
 7. A method according toclaim 6 wherein the low-density sold particulate material comprises from0.1 to about 6% by weight of the total solid or structural gelformulation.
 8. A method according to claim 1 wherein the low-densitysolid particulate material has a volume mean diameter below 100 microns.9. A method according to claim 8 wherein the low-density solidparticulate material has a volume mean diameter of from 20 to 50microns.
 10. A method according to claim 1 wherein the water-soluble orwater-dispersible solid or structured gel formulation contains awater-dispersible or water soluble filler.